Mold release material for die castings

ABSTRACT

The mold release material for die castings is such one that an emulsion based on animal or vegetable oils, mineral oil, fatty acid and esters thereof is added an alkali metal or alkali earth metal salt of EDTA in the range 10-10,000 ppm. The alkali metal or alkali earth metal salt of EDTA prevents the aqueous solution of emulsion of the mold release material of the invention from micell formation, forms a stable emulsion, is scarcely affected by temperature, and forms bivalent metal ion and water soluble complex whereby it does not form deposits even if hard water is used as diluted water of the mold release material.

INDUSTRIAL FIELD OF THE INVENTION

This invention relates to an improvement in a mold release material fordie castings.

PRIOR ART

Known mold release materials for die castings are ones based on animaland vegetable oils or mineral oil and to which base material is addedfatty acid, paraffin wax, silicone oil, graphite and the like to giveheat resistance. However, it is known that though such additives maypresent a mold release material of high heat resistance, adding onlyfatty acid or paraffin wax causes an increase of viscosity of the moldrelease material emulsion or causes difficulties in automatic sprayingof the material. Adding silicone oil or graphite either causes defectsin the product such as crimp or blow holes as a result of the residualsolids remaining in the die casting mold or pollutes the mold.

On the other hand, mold release materials for die castings, which areadded with solids, are also commercially available. However, where theyare used by automatic spraying under a centralized piping feed system,they cause clogging of the nozzle of the automatic spray and workingdifficulties.

The mold release material of the present invention does not useadditives such as silicone oil and graphite which generate residualsolids in the die casting mold, and its bases comprise only one or moreof animal and vegetable oils, mineral oil, fatty acid and estersthereof. As a result, it does not cause pollution of the die castingmold by silicone oil or graphite, E contamination of the workingenvironment by graphite, or any other public nuisance since the wastewater can be easily disposed.

However, water-soluble emulsions constituted only of fats and fatty oilhave drawbacks in that the viscosity of the aqueous solution greatlyvaries. There is a large increase in viscosity as the temperature of thesolutions rises, and in an extreme case, the aqueous solutiongelatinizes.

DISCLOSURE OF THE INVENTION

To achieve the above objects, in the mold release material of theinvention to an emulsion based on one or more of animal and vegetableoils, mineral oil, fatty acid and ester thereof is added an alkali metalor alkaline earth metal salt of ethylenediaminetetraacetic acid(hereinafter referred to as alkali metal or alkaline earth metal salt ofEDTA).

The inventor of this invention has conducted extensive research in anattempt to produce and provide a new mold release material for diecastings, and as a result he has found that an alkali metal or alkalineearth metal salt of EDTA prevents the aqueous solution of emulsions ofthese mold release materials from micell formation, forms a stableemulsion that is hardly affected by temperature, and even enables use ofhard water as the diluted water of the mold release material to formbivalent metal ion and water soluble complexes that do not formdeposits.

BEST EMBODIMENTS TO CARRY OUT THE INVENTION

As described above, the mold release materials for die castings relatingto this invention form a stable emulsion by adding to the components ofthe material an alkali metal or alkaline earth metal salt of EDTA in therange of 10-10,000 ppm. Further, it is confirmed that the addition ofalkali metal or alkaline earth metal salt of EDTA does not adverselyaffect the mold release effect of the material for die castings. Todescribe the effect of the invention more definitely, an Example formolding a die casting of an aluminum alloy is mentioned below.

If the alkali metal or alkaline earth metal salt of EDTA is added atless than 10 ppm, the effect of the additive is not noticed. If morethan 10,000 ppm of the additive is added, an improvement in the effectis not confirmed either.

Below is mentioned an Example of the invention, which uses EDTA-4Na, arepresentative example of an alkali metal or alkaline earth metal saltof EDTA.

EXAMPLE

The following composition was obtained as a mix of the mold releasematerial for die castings according to the invention.

    ______________________________________                                        Fatty acid quaternary ammonium salt                                                                  18%                                                    Hydrocarbon            22%                                                    Polyoxyethylene alkyl ether                                                                          30%                                                    Fatty acid glycerol ester                                                                            10%                                                    Water                  28%                                                    ______________________________________                                    

The above mix was diluted threefold and 300 ppm of EDTA-4Na was added,and the change in viscosity was measured in comparison with products towhich the additive was not added. The values of the viscosity change areshown in Table 1.

                  TABLE 1                                                         ______________________________________                                        Viscosity change (cp) by EDTA-4Na                                             Temperature                                                                   (°C.)                                                                           5       10     20   30   40    50   60                               ______________________________________                                        Not added                                                                              240     250    300  500  1,200 6,000                                                                              70,000                           Added by  65      45     30   30    30    30    30                            300 ppm                                                                       ______________________________________                                    

Further, the above mix was diluted by 2.5 times and the additive amountof EDTA-4Na was changed to measure the change of the viscosity. Thevalues in the viscosity change are shown in Table 2.

                  TABLE 2                                                         ______________________________________                                        Additive                                                                      amount (ppm)                                                                  of EDTA-4Na                                                                             0         10     300    1,000                                                                              10,000                                 ______________________________________                                        Viscosity (cp)                                                                          7,540     3,800  428    200  47                                     ______________________________________                                    

The above mix was diluted threefold and 300 ppm of EDTA-4Na was added toprepare a specimen. When used the specimen was diluted by 80 times, andan injection molding was effected using an aluminum alloy (JIS: ADS-12).

Machine used: 350t die casting machine

Material: ADC-12

Melt temperature: 680° C.

Product: Transmission oil seal for motor vehicles

    ______________________________________                                                     Product of                                                                             Commercially                                                         this invention                                                                         available article                                       ______________________________________                                        Shot frequency until                                                                         3,500      1,800                                               the mold is required                                                          for polishing                                                                 Surface of product                                                                           Excellent  Good                                                Raton (%) of      1          2                                                inferior quality                                                              products                                                                      ______________________________________                                    

As described above in detail, the present invention provides theemulsion of mold release material for die castings with excellentstability, is constituted of a substance that deposits residue to thedie casting mold, and, therefore, provides excellent working properties.

Use of other alkali metals or alkaline earth metal salts of EDTA givealmost the same results.

Moreover, by changing the kind of animal or vegetable oil used, it isalso possible to control the amount of residual carbon of the moldrelease material for die castings, and it has an advantage of flexiblycoping even with the dimension of the die casting machine.

INDUSTRIAL APPLICATION EASIBILITY

Though the mold release material of the present invention has beendescribed with regard to the die castings of an aluminum alloy, it canachieve the same functional effect even when used as the mold releasematerial for die castings of aluminum, magnesium or alloys thereof, andzinc and alloys thereof.

I claim:
 1. A mold release material for die castings comprising anemulsion of at least one of selected from the group consisting ofmineral oil and fatty acid and esters thereof having added thereto from10 to 10,000 ppm of an alkali metal or alkaline earth metal salt ofethylenediaminetetraacetic acid.
 2. The mold release material of claim 1wherein said fatty acid ester is at least one selected from the groupconsisting of animal oils and vegetable oils.